rustc_attr_parsing/
validate_attr.rs

1//! Meta-syntax validation logic of attributes for post-expansion.
2
3use std::convert::identity;
4use std::slice;
5
6use rustc_ast::token::Delimiter;
7use rustc_ast::tokenstream::DelimSpan;
8use rustc_ast::{
9    self as ast, AttrArgs, AttrKind, Attribute, DelimArgs, MetaItem, MetaItemInner, MetaItemKind,
10    Safety,
11};
12use rustc_errors::{Applicability, Diagnostic, PResult};
13use rustc_feature::BUILTIN_ATTRIBUTE_MAP;
14use rustc_hir::AttrPath;
15use rustc_parse::parse_in;
16use rustc_session::diagnostics::report_lit_error;
17use rustc_session::lint::builtin::ILL_FORMED_ATTRIBUTE_INPUT;
18use rustc_session::parse::ParseSess;
19use rustc_span::{Span, Symbol, sym};
20
21use crate::{AttributeParser, AttributeTemplate, session_diagnostics as errors, template};
22
23pub fn check_attr(psess: &ParseSess, attr: &Attribute) {
24    use ast::SyntheticAttr::*;
25    match &attr.kind {
26        AttrKind::Normal(_) => {}
27        AttrKind::Synthetic(CfgTrace(_) | CfgAttrTrace) | AttrKind::DocComment(..) => return,
28    }
29
30    let builtin_attr_info = attr.name().and_then(|name| BUILTIN_ATTRIBUTE_MAP.get(&name));
31
32    // Check input tokens for built-in and key-value attributes.
33    if let Some(name) = builtin_attr_info {
34        if AttributeParser::is_parsed_attribute(slice::from_ref(name)) {
35            return;
36        }
37        match parse_meta(psess, attr) {
38            // Don't check safety again, we just did that
39            Ok(meta) => {
40                // FIXME The only unparsed builtin attributes that are left are the lint attributes, so we can hardcode the template here
41                let lint_attrs = [sym::forbid, sym::allow, sym::warn, sym::deny, sym::expect];
42                if !lint_attrs.contains(name) {
    ::core::panicking::panic("assertion failed: lint_attrs.contains(name)")
};assert!(lint_attrs.contains(name));
43
44                let template = crate::AttributeTemplate {
    word: false,
    list: Some(&["lint1", "lint1, lint2, ...",
                    r#"lint1, lint2, lint3, reason = "...""#]),
    one_of: &[],
    name_value_str: None,
    docs: Some("https://doc.rust-lang.org/reference/attributes/diagnostics.html#lint-check-attributes"),
}template!(
45                    List: &["lint1", "lint1, lint2, ...", r#"lint1, lint2, lint3, reason = "...""#],
46                    "https://doc.rust-lang.org/reference/attributes/diagnostics.html#lint-check-attributes"
47                );
48                check_builtin_meta_item(psess, &meta, attr.style, *name, template, false)
49            }
50            Err(err) => {
51                err.emit();
52            }
53        }
54    } else {
55        let attr_item = attr.get_normal_item();
56        if let AttrArgs::Eq { .. } = attr_item.args {
57            // All key-value attributes are restricted to meta-item syntax.
58            match parse_meta(psess, attr) {
59                Ok(_) => {}
60                Err(err) => {
61                    err.emit();
62                }
63            }
64        }
65    }
66}
67
68pub fn parse_meta<'a>(psess: &'a ParseSess, attr: &Attribute) -> PResult<'a, MetaItem> {
69    let item = attr.get_normal_item();
70    Ok(MetaItem {
71        unsafety: item.unsafety,
72        span: attr.span,
73        path: item.path.clone(),
74        kind: match &item.args {
75            AttrArgs::Empty => MetaItemKind::Word,
76            AttrArgs::Delimited(DelimArgs { dspan, delim, tokens }) => {
77                check_meta_bad_delim(psess, *dspan, *delim);
78                let nmis =
79                    parse_in(psess, tokens.clone(), "meta list", |p| p.parse_meta_seq_top())?;
80                MetaItemKind::List(nmis)
81            }
82            AttrArgs::Eq { expr, .. } => {
83                if let ast::ExprKind::Lit(token_lit) = expr.kind {
84                    let res = ast::MetaItemLit::from_token_lit(token_lit, expr.span);
85
86                    match res {
87                        Ok(lit) => {
88                            if token_lit.suffix.is_some() {
89                                let mut err = psess.dcx().struct_span_err(
90                                    expr.span,
91                                    "suffixed literals are not allowed in attributes",
92                                );
93                                err.help(
94                                    "instead of using a suffixed literal (`1u8`, `1.0f32`, etc.), \
95                                    use an unsuffixed version (`1`, `1.0`, etc.)",
96                                );
97                                return Err(err);
98                            }
99                            MetaItemKind::NameValue(lit)
100                        }
101                        Err(err) => {
102                            let guar = report_lit_error(psess, err, token_lit, expr.span);
103                            let lit = ast::MetaItemLit {
104                                symbol: token_lit.symbol,
105                                suffix: token_lit.suffix,
106                                kind: ast::LitKind::Err(guar),
107                                span: expr.span,
108                            };
109                            MetaItemKind::NameValue(lit)
110                        }
111                    }
112                } else {
113                    // Example cases:
114                    // - `#[foo = 1+1]`: results in `ast::ExprKind::Binary`.
115                    // - `#[foo = include_str!("nonexistent-file.rs")]`:
116                    //   results in `ast::ExprKind::Err`. In that case we delay
117                    //   the error because an earlier error will have already
118                    //   been reported.
119                    let msg = "attribute value must be a literal";
120                    let mut err = psess.dcx().struct_span_err(expr.span, msg);
121                    if let ast::ExprKind::Err(_) = expr.kind {
122                        err.downgrade_to_delayed_bug();
123                    }
124                    return Err(err);
125                }
126            }
127        },
128    })
129}
130
131fn check_meta_bad_delim(psess: &ParseSess, span: DelimSpan, delim: Delimiter) {
132    if let Delimiter::Parenthesis = delim {
133        return;
134    }
135    psess.dcx().emit_err(errors::MetaBadDelim {
136        span: span.entire(),
137        sugg: errors::MetaBadDelimSugg { open: span.open, close: span.close },
138    });
139}
140
141/// Checks that the given meta-item is compatible with this `AttributeTemplate`.
142fn is_attr_template_compatible(template: &AttributeTemplate, meta: &ast::MetaItemKind) -> bool {
143    let is_one_allowed_subword = |items: &[MetaItemInner]| match items {
144        [item] => item.is_word() && template.one_of.iter().any(|&word| item.has_name(word)),
145        _ => false,
146    };
147    match meta {
148        MetaItemKind::Word => template.word,
149        MetaItemKind::List(items) => template.list.is_some() || is_one_allowed_subword(items),
150        MetaItemKind::NameValue(lit) if lit.kind.is_str() => template.name_value_str.is_some(),
151        MetaItemKind::NameValue(..) => false,
152    }
153}
154
155pub fn check_builtin_meta_item(
156    psess: &ParseSess,
157    meta: &MetaItem,
158    style: ast::AttrStyle,
159    name: Symbol,
160    template: AttributeTemplate,
161    deny_unsafety: bool,
162) {
163    if !is_attr_template_compatible(&template, &meta.kind) {
164        // attrs with new parsers are locally validated so excluded here
165        emit_malformed_attribute(psess, style, meta.span, name, template);
166    }
167
168    if deny_unsafety && let Safety::Unsafe(unsafe_span) = meta.unsafety {
169        psess.dcx().emit_err(errors::InvalidAttrUnsafe {
170            span: unsafe_span,
171            name: AttrPath::from_ast(&meta.path, identity),
172        });
173    }
174}
175
176pub fn emit_malformed_attribute(
177    psess: &ParseSess,
178    style: ast::AttrStyle,
179    span: Span,
180    name: Symbol,
181    template: AttributeTemplate,
182) {
183    // Some of previously accepted forms were used in practice,
184    // report them as warnings for now.
185    let should_warn = |name| #[allow(non_exhaustive_omitted_patterns)] match name {
    sym::doc | sym::link | sym::test | sym::bench => true,
    _ => false,
}matches!(name, sym::doc | sym::link | sym::test | sym::bench);
186
187    let error_msg = ::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("malformed `{0}` attribute input",
                name))
    })format!("malformed `{name}` attribute input");
188    let mut suggestions = ::alloc::vec::Vec::new()vec![];
189    let inner = if style == ast::AttrStyle::Inner { "!" } else { "" };
190    if template.word {
191        suggestions.push(::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("#{0}[{1}]", inner, name))
    })format!("#{inner}[{name}]"));
192    }
193    if let Some(descr) = template.list {
194        for descr in descr {
195            suggestions.push(::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("#{0}[{1}({2})]", inner, name,
                descr))
    })format!("#{inner}[{name}({descr})]"));
196        }
197    }
198    suggestions.extend(template.one_of.iter().map(|&word| ::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("#{0}[{1}({2})]", inner, name,
                word))
    })format!("#{inner}[{name}({word})]")));
199    if let Some(descr) = template.name_value_str {
200        for descr in descr {
201            suggestions.push(::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("#{0}[{1} = \"{2}\"]", inner, name,
                descr))
    })format!("#{inner}[{name} = \"{descr}\"]"));
202        }
203    }
204    // If there are too many suggestions, better remove all of them as it's just noise at this
205    // point.
206    if suggestions.len() > 3 {
207        suggestions.clear();
208    }
209    if should_warn(name) {
210        let suggestions = suggestions.clone();
211        psess.dyn_buffer_lint(
212            ILL_FORMED_ATTRIBUTE_INPUT,
213            span,
214            ast::CRATE_NODE_ID,
215            move |dcx, level| {
216                crate::diagnostics::IllFormedAttributeInput::new(&suggestions, template.docs, None)
217                    .into_diag(dcx, level)
218            },
219        );
220    } else {
221        suggestions.sort();
222        let mut err = psess.dcx().struct_span_err(span, error_msg).with_span_suggestions(
223            span,
224            if suggestions.len() == 1 {
225                "must be of the form"
226            } else {
227                "the following are the possible correct uses"
228            },
229            suggestions,
230            Applicability::HasPlaceholders,
231        );
232        if let Some(link) = template.docs {
233            err.note(::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("for more information, visit <{0}>",
                link))
    })format!("for more information, visit <{link}>"));
234        }
235        err.emit();
236    }
237}
rustc_attr_parsing/validate_attr.rs

rustc_attr_parsing/
validate_attr.rs
